Can anyone help plz

got a bit of a problem

was installing a webcam on pc , followed instrutions and let it install the driver and software , waited for it to tell me to reboot the comp , the comp then seemed to freeze up and took about 5 mins to shut down before rebooting , when rebooted it told me to plug camera into usb port which i did , it went to install ,and told me there was a problem installing the device or something those words , anyway i then went to my comp , right clicked , properties , hardware devices , device manager so that i could remove the driver etc , wen getting there , it was empty so i could not see any of my devices , i then went to my computer and it was also blank , then up popped a torch shining over a folder looking for the bits that should be there , is there anyway that i can get things back to the way they should be without formatting the comp ,

ps ive done a chkdsk and that was ok dint have no bad sectors on h/d
also cant use anything that is usb , ie printer , usb flash drive , the card progger looks as if it is ok as the light is on as it should be , and when launch the software it checks for updates , but when try to do a card , it just comes up with cannot write data

thx in advance for any help